The discussion of any work, publications, sales, or activity anywhere in this submission, including in any documents submitted with this application, shall not be taken as an admission that any such work constitutes prior art. The discussion of any activity, work, or publication herein is not an admission that such activity, work, or publication existed or was known in any particular jurisdiction.
Series connected lighting systems were a popular form of municipal street lighting for many decades in the U.S. In a typical series system, as illustrated in FIG. 1, each lamp is connected in series along one line. Among several reasons for such systems was the even distribution of available current across the load and the control of the entire lighting system from one central location, and various technological limitations at the time, such as the lack of affordable photo-controls.
In the most basic version of such systems a burn-out or absence of a light at one point in the series causes an open circuit and all the lights on that series go dark. A number of prior art improvements were directed to providing a system wherein failure of one of the loads would not interrupt the power to the remaining loads. For example, systems have incorporated various forms of shorting circuits which shunt each lamp. When a lamp fails resulting in an open circuit, the shorting circuit is activated and places a short across the failed lamp thereby completing the circuit and allowing current to flow to the remaining lamps. For example, U.S. Pat. Nos. 1,024,495 and 2,809,329 discuss series connected lamps shunted by shorting circuits.
In other systems, to avoid shorting circuits, each lamp is connected to a different isolation transformer secondary winding. The transformer primary windings are connected in series to the main power source. Thus, because in this circuit, each lamp is connected to a transformer secondary winding, if a lamp fails the power to the other lamps is not interrupted. However, this approach can lead to a bulky circuit and high cost. Another power circuit arrangement is in U.S. Pat. No. 3,969,649, which discusses a bicycle lighting system including two lamps connected in series across a winding of a dynamo. An impedance is connected between an internal tap of the winding and a junction point between the lamps. The impedance is selected to establish system equilibrium whereby the lamp junction point and tap are maintained at the same potential under normal operating conditions despite variations in dynamo and lamp resistance with bicycle speed. If a lamp fails resulting in an open circuit, the power to the remaining lamp is not interrupted.
Despite the above, however, there has been no system allowing a 6.6 AMP type light system to use standard light lamps or fixtures that require effectively constant voltage power supply.